Search

MXene, which is known for its high electrical/thermal conductivity, surface hydrophilicity, excellent mechanical flexibility, and chemical stability, is a versatile and smart material for soft actuators. However, most MXene actuators are fabricated by combining MXene with other inert materials to form a bilayer or multilayer structure. Considering the strain mismatch at multimaterial interfaces under frequent deformation, MXene‐based actuators are generally associated with poor stability, which limits their practical applications. Herein, inspired by the natural quantum‐confined superfluidic (QSF) effect, a multiresponsive MXene actuator that can be driven by moisture, light, and electricity by engineering an asymmetric QSF structure on both sides of the MXene film is reported. The actuation mechanism of the MXene film can be attributed to nonuniform water adsorption, transport, and desorption within the asymmetric QSF channels under moisture, photothermal, and electrothermal stimuli. Interestingly, MXene actuators can be flexibly formed into various shapes under moisture‐assisted mechanical compression, which not only enhances their multiresponsive actuation, but also permits a more complex deformation. As proof‐of‐concept demonstrations, various intriguing applications including a dual‐role robot, a smart shielding curtain, and a dragonfly robot, are fabricated, revealing the potential of MXene actuators for soft robotics. [ABSTRACT FROM AUTHOR]

Fluorescent hydrogels have emerged as one of the most promising candidates for developing biomimetic materials and artificial intelligence owing to their unique fluorescence and responsive properties. However, it is still challenging to fabricate hydrogel that exhibits synergistic changes in fluorescence color and shape in response to multistimulus via a simple method. Herein, blue‐ and orange‐emitting fluorescent microgels (MGs) both are designed and synthesized with pH‐, thermal‐, and cationic‐sensitivity via one‐step polymerization, respectively. The two fluorescent MGs are incorporated into transparent doubly crosslinked microgel (DX MG) hydrogels with a preset ratio. The DX MG hydrogels can tune the fluorescent color accompanied by size variation via subjecting to external multistimulus. Thus, DX MG hydrogels can be exploited for multiresponsive fluorescent bilayer actuators. The actuators can undergo complex shape deformation and color changes. Inspired by natural organisms, an artificial morning glory with color and size changes are showcased in response to buffer solutions of different pH values. Besides, an intelligent skin hydrogel, imitating natural calotes versicolor, by assembling four layers of DX MG with different ratios of MGs, is tailored. This work serves as an inspiration for the design and fabrication of novel biomimetic smart materials with synergistic functions. [ABSTRACT FROM AUTHOR]

Light emission from CaZnOS:Nd3+ by high‐intensity ultrasound excitation is demonstrated. Acoustic power and duty ratio enable simultaneous control of the degree of (local) thermo‐acoustic heating in isothermal or nonisothermal conditions. The Nd‐related photoemission provides direct thermometric feedback at an absolute sensitivity on the order of 10−4 K−1, within the physiological temperature range. From the individual temperature dependence of persistent luminescence and mechanoluminescence, both effects are attributed to a heterologous de‐trapping mechanism. In addition to acoustic heating and optical thermometry, this enables optical information storage and smart labeling with optoacoustic read‐out. [ABSTRACT FROM AUTHOR]

Light emission from CaZnOS:Nd3+ by high‐intensity ultrasound excitation is demonstrated. Acoustic power and duty ratio enable simultaneous control of the degree of (local) thermo‐acoustic heating in isothermal or nonisothermal conditions. The Nd‐related photoemission provides direct thermometric feedback at an absolute sensitivity on the order of 10−4 K−1, within the physiological temperature range. From the individual temperature dependence of persistent luminescence and mechanoluminescence, both effects are attributed to a heterologous de‐trapping mechanism. In addition to acoustic heating and optical thermometry, this enables optical information storage and smart labeling with optoacoustic read‐out. [ABSTRACT FROM AUTHOR]

The potential to improve mechanical, structural, and mechanochemical properties of charge‐functionalized poly(N,N‐dimethylaminoethyl methacrylate) (PDMAEMA)‐based hybrid cryogels is investigated. The simple and versatile synthesis of hybrid cryogels with high strength and toughness using cationic DMAEMA and ionic comonomer 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid has been proposed via in situ free‐radical crosslinking (cryo)polymerization by which the properties of virgin polymer can be modulated to required applications by incorporation of inorganic filler kaolin (KLN). Two factors affecting swelling and elasticity of hybrid gels (referred as PDA/KLNm), KLN content and gel preparation temperature, are studied. The optimum KLN concentration for desired swelling and modulus of elasticity is determined as 0.80% (w/v). Effective crosslinking density of hybrid hydrogels increases with KLN addition and this dependence is expressed by a quadratic polynomial as a function of KLN concentration. The results show that obtained hybrid gels with multiresponsive properties could be regarded as "smart materials" in sensing and actuation applications. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1758–1778 [ABSTRACT FROM AUTHOR]